1. Field of the Invention
The invention relates to apparatuses and processes for producing a honeycomb body having a multiplicity of at least partially structured sheet metal layers which form a multiplicity of passages through which a fluid can flow.
Catalyst carrier bodies are used to deal with the progressively increasing strictness of the provisions relating to the emission of pollutants, in particular from motor vehicles. Such catalyst carrier bodies may involve metallic honeycomb bodies. Such a honeycomb body includes, for example, a stack of a multiplicity of at least partially structured sheet metal layers. The stack is intertwined or twisted in opposite directions about itself and about a central region. Such a honeycomb body structure is known, for example, from U.S. Pat. No. 4,923,109. International Patent Publication WO 90/03220, corresponding to U.S. Pat. Nos. 5,139,844; 5,105,539 and 5,135,794, discloses a metallic catalyst carrier body for motor vehicles, which is made up of at least partially structured sheet metal layers. That catalyst carrier body includes at least three stacks of sheet metal layers, wherein at least three of the stacks are folded around a respectively associated bend line in the central region of the honeycomb body and in the folded condition are intertwined in the same direction around each other and around the central region with the bend lines.
Apparatuses which are known for producing such catalyst carrier bodies include a fork-shaped intertwining device that is rotatable about a central axis and which engages each stack, and former segments that close to form a former. The inner cross-section of the closed former corresponds to the cross-section of the honeycomb body in the wound condition. The most frequent form in which the honeycomb bodies are constructed is cylindrical. In order to ensure that the stacks are intertwined around themselves and around a central region, the former segments are moved towards the stack in such a way that during the rotary movement of the fork-shaped intertwining device, the stack or stacks bear against an edge of the former segments and that edge forms a support device. Towards the end of the production procedure the former is completely closed and thus imparts its definitive form to the honeycomb body.
The structural expenditure on such an apparatus is relatively high by virtue of the fact that the former includes two former segments which are movable towards and away from each other. During such a production process it is always necessary to ensure that the former segments move with a predetermined sequence of movements. Due to abrasion wear, dust or the like, guides of the former segments may suffer from receiving deposits therein, which can interfere with the movements that are involved.
In the known apparatuses for the production of a honeycomb body, in particular a catalyst carrier body, there is a danger of at least one former segment moving during the closing operation in opposite relation to the direction of movement of the portion of a stack which is still to be intertwined. When the former segment presses against the portion of the stack, that can give rise to undesired deformation of the stack or stacks. Deformation of the stack has the result of causing individual sheet metal layers to be partially bent. The structure of the finished honeycomb body is adversely affected thereby. On one hand the strength of the honeycomb body suffers and on the other hand the passage cross-sections experience a local change. The result of a change in the passage cross-sections is that it is no longer possible to guarantee a uniform flow distribution within the honeycomb body. However, the flow profile of an exhaust gas through a catalyst carrier body is a decisive factor in terms of the catalytic action of the catalytic converter.